Contents

GSK Thienopyrimidine Series

Preamble

This page describes the current status of one of three antimalarial drug candidates being investigated by the Todd laboratory at the University of Sydney, using a strictly open source approach. A more thorough discussion of this approach may be found at: OSDDMalaria:Story so far.

The drug development being performed in this project is open source. Such an approach involves adherance to the six laws of open source science.

1) First law: All data are open and all ideas are shared
2) Second Law: Anyone can take part at any level of the project
3) Third Law: There will be no patents
4) Fourth Law: Suggestions are the best form of criticism
5) Fifth Law: Public discussion is much more valuable than private email
6) Sixth Law: The project is bigger than, and is not owned by, any given lab. The aim is to find a good drug for malaria, by whatever means, as quickly as possible.

All experimental work in this project is described on an open lab book; status updates for the project are posted on the synaptic leap; and some discussions take place on Google+ and Twitter where convinient. All are publicly viewable and, once a member of the relevant platforms (eg: Facebook), anyone may discuss the project in the open. All discussion, suggestions, complaints and queries are welcome. If a more private avenue for discussion is required, several personal contact points are to be found at User:Jim Cronshaw and at User:Matthew Todd.

The Origin of this Antimalarial Drug Candidate

In 2010, GlaxoSmithKline released chemical and biological data pertaining to some 13,500 compounds that displayed potent antimalarial activity in vitro (Nature paper). Medicinal chemists at the Medicines for Malaria Venture identified two compounds present in this dataset which they believed to be excellent antimalarial drug candidates. These two compounds had the combination of a drug-like profile (polar, low molecular weight, amenable to structural variation), low poteny, low cytotoxicity, no known IP issues, and to the best of their knowledge, they were not the subject of antimalarial research anywhere else in the world. One of these compounds is the subject of this wiki entry, and is termed here the "aminothienopyrimidine series".

Known Data

The first structure in this series, | TCMDC 135294, has the following structure:

Of all structures on the GSKTCAMS that have the aminothienopyrimidine moiety, this molecule has the most attractive ALogP value and the lowest molecular weight (search performed by Jim Cronshaw 5/8/12 on ChemblNTD). We therefore argue that this compound is an excellent starting point for a lead development campaign, pending confirmation of the compound's antimalarial activity. This compound must be synthesised anew and fully characterised before submitting it for an in vitro screen against the parasite. If the compound displays potent antimalarial activity then a lead development campaign will begin.

Synthesis

The proposed synthesis for this compound is below:

Proposed synthesis for the above compound

Alternatives

The step that involves n-BuLi would best be avoided, and if a more direct route of arriving at the Suzuki coupling step could be discovered, that would take a potentially dangerous and difficult step out of the synthetic route.

One possibility, involving NIS and an ionic liquid such as 1-Butyl-3-methylimidazolium tetrafluoroborate (which our lab doesn't have, but which is available from Aldrich in catalytic quality from $247/5g), is found below:

[doi:10.1016/j.tetlet.2011.03.010 DOI]

[dx.doi.org/10.1139/V09-125 Here] is another alternative, where the direct iodonation of arenes can be carried out using oxone and NaI. Whether or not this would work in my compound, given selectivity issues, is something that I'll have to investigate.

This paper shows a method of direct halogenation of thiophenes. This uses [Bis(trifluoroacetoxy)iodo]benzene, which we don't have lying around, but which can be bought from Aldrich for $136/10g. The reactivity of thiophenes vs pyrimidines is something I'll have to look into. UPDATE: I've read Clayden et al. (2012, p 727) and I'm informed that pyridine is, generally speaking, terrible at electrophilic aromatic substitution reactions. My understanding is that pyrimidine has the same reactivity as does pyridine, so there shouldn't be any selectivity problems with any of these reactions (a result that was perhaps anticipated by the BuLi reaction proceeding at the alpha position on the thiophene ring in the first place).

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July 9th.

The BuLi reactions have literature precedent. Heffron (2010) acheives a very similar reaction, albeit with protection of a pyrimidine position (which doesn't seem to be reacting in my case anyway). Snegaroff (2009) uses (TMP)3CdLi to acheive the metallation/iodination. This less harsh base can be used at rt. This author discovered the reagent, so they are probably interested in self promotion. In any case, there is precedent for the lithium metallation proceeding.

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July 18th

A post on ChemForums suggested that the sulfur might react with the iodine. According to Joule & Mills (p. 234) this won't happen. "The five membered heterocycles do not react with electrophiles at the heteroatom." and "...in pyrrole, electrophilic addition at the nitroge would lead to a substantial loss of resonance stabilisation - the molecule would be converted into a cyclic butadiene, with an attached nitrogen carrying a positive charge localised on that nitrogen atom.

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August 26

A search performed on SciFinder at 8:57pm revealed that the meta sulfonamide is NOT novel.

Thiophene Starting Material Synthesis

Additionally, the thiophene available from Sigma Aldrich for $159/10g can be made from the following synthesis.

Proposed synthesis for the above compound

Analogues

TCMDC 135294 is part of a series with one other member, | TCMDC 135255, shown below:

A list of commercially available compounds with similar structures to the one I'm trying to synthesise were identified with much help from Iain Wallace. If you're reading this and are interested in donating samples of these compounds, feel free to contact me: Jim Cronshaw

Iain Wallace created a cytoscape file which details purchaseable compounds related to the two series that I am trying to make. The file can be found here, and Cytoscape can be downloaded for free here (one will need to activate the chemviz plugin, which can be activated from within Cytoscape). The results of this work, in the form of a list of purchaseable compounds, can be found here

A list of the above compounds in .csv format, with InChi, InChiKey, SMILES and eMolecules identifiers, can be found here.